The ignition switch bolts to the back of the key cylinder. There is a rectangular wire connector attached to it.
Interchange
Ignition Switch Comparison
B310 has a larger-diameter switch with two mounting lugs. B110 is smaller with one mounting lug. I believe the middle one (the one with the wiring harness) is a B210 switch, and looks like it would plug into the B110 harness, but is wired differently. Beware! I think this is the B210 Auto harness, where the BY wire goes through the auto-trans shifter inhibit switch (can only start car when in Nuetral or Park).
The 1971 switch has four spade terminals. The 1972 and newer adds the "Accessory" position and so has five spade terminals.
TIP: On the back of the switch, each contact is marked ('S', 'IG', etc.). Double-check before replacing to ensure they are the same.
B110 & B210 North American Wiring
| W | B (Battery) |
| BW or | IG (ignition/Run) |
| BW (LW for B210) | ACC (Accessory)
1971 switches didn't have ACC position |
| BY (YB for B210) | S (start) |
BR | R (resistor) | </tr>
The switch in the picture with the wires has differently colored wires (WR, L, BL, BW, BY). From these colors and position, I think it is the same wiring as the B310 switch, just different colors.
Wiring
Switch internal connections
| Off | no connections |
| Accessory | Battery (hot) to ACC |
| Run | Battery (hot) to ACC + IG |
| Start | Battery (hot) to IG + Resistor + Start\* |
\*Starting with 1974 automatic models and all newer, ACC is also hot while in the Start position.
Where do the wires go on a stock B110?
| switch terminal | Connects to ... |
| IG (ignition/run) | This connects to two things:- Directly to Ballast Resistor (non-coil side). This is spelled "Resister" in some Nissan publications. If equipped with optional factory tachometer, this circuit goes through tachometer
<li>To IG circuit of fuse box</ul></td></tr>
| S (start) | <li>the solenoid on the starter
On automatic cars*, this goes through the "Nuetral Switch". |
| B (battery/hot) | <li>battery + terminal, through the fusible link
<li>Fuse box "B" side
<li>Alternator "A" large output wire
<li>Voltage regulator "A" terminal |
| R (resistor) | <li>Coil + terminal
<li>Ballast resistor (coil side) |
| ACC (accessory) | <li>Radio (through inline fuse)
Since 1971 didn't get ACC position, 1971 radios connect to fuse box L wire (always hot)
<li>Optional heated rear window glass
<li>Note that this circuit does NOT go to the fuse box, as does Bat and IG |
</table>
\*Automatics became available in 1973 in North America.
 Lock Comparison - No ACC position for 1971
(the two wires at the front of the cylinder are for the Warning Buzzer system)
Common Problems
Ever had the "sometime it doesn't start until I turn the key back and forth a few times" problem? This occurs because the relatively high current loads of the starter solenoid tend to burn the ignition switch Start contacts after some years. This only gets worse. You might think you could prevent this problem by using a relay. The S wire could go to to a relay, and the relay could go from the Main Fuse to the starter. The problem is if the relay sticks, you won't be able to turn it off with the key. To prevent this, you could use two relays, with the main power fed through a relay connected to the IG terminal of the switch. Then if the starter relay sticks, you could turn key to ACC or OFF to stop it.
Easiest just to replace the switch. Which other Datsun (or other brand) cars use the same switch? Click Edit and add to this list.
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